1. Field of the Invention
The present invention relates to a content distribution system whereby digital content data such as video and music produced by a content provider is distributed from a server device of a service provider via communication or a broadcast so that a terminal device of an end user uses the digital content. Hereafter, this content distribution system may be referred to as a B2B2C (Business to Business to Consumer) system according to the circumstances. As mentioned above, the B2B2C system is an abbreviation indicating a relation among a content provider (Business) that creates products, a service provider (Business) that sells them, and an end user (Consumer) that purchases them. The present invention particularly relates to a right management terminal that is used for copyright protection for content in the B2B2C system.
2. Description of the Related Art
In recent years, content distribution service, by which the digital content such as video and music (simply referred to as content, hereafter) is distributed from the server device to the terminal device via communication or a broadcast so that the terminal device uses the content, is entering its commercial stage. Meanwhile, it becomes easy to make unauthorized duplication of content due to the development of digital equipment. This increases problems associated with copyright infringement. On account of this, the content distribution service employs a copyright protection technology (DRM: Digital Rights Management) for the purpose of preventing the unauthorized usage of content. Using the cryptographic technology and the authentication technology, the copyright protection technology allows only an authorized user to use content within a predetermined range. To be more specific, the server device of the content provider encrypts the content, then distributes the encrypted content to the terminal device of the end user. Moreover, the terminal device obtains a sales license that includes a content key to decrypt the encrypted content and a usage condition of the content (such as the number of usage times and a period of validity) from the server device of the service provider. In accordance with the usage condition included in the received sales license, the terminal device decrypts the encrypted content to use the content. By means of the method described so far, the content is protected and the unauthorized usage of the content is prevented.
Here, since the above-mentioned sales license is generated by the server device of the service provider, the information inside the license such as the content key and the usage condition is set by the service provider. Meanwhile, because the service provider needs to use the content key that was made by the content provider in the encryption processing performed on the content, the content key can be considered as the information that can be substantially controlled by the content provider. In addition, by means of the method as disclosed in Japanese Application Patent Publication No. 8-329011, even though the content provider controls the content key, the service provider can edit the content received from the content provider and distribute the edited, encrypted content to the terminal device of the end user.